DESCRIPTION (adapted from application abstract): Many sexually transmitted diseases (STDs) including HIV infection are transmitted in single-event or brief partnerships, however, many also occur and reoccur within established partnerships. Most if not all HIV/AIDS/STD-related behavioral interventions to date have focused on individual level or to a lesser extent - group or community level interventions. However, interventions focusing on changing the sexual behavior of partnerships represent an alternative or complementary approach that has been largely neglected until now. Development of partnership-level behavior change requires knowledge of patterns of behavior within partnerships and of how patterns vary by the stage of the partnership. In particular, the individuals` choices about their own behavior is limited by the control exerted (overt or covert) by their sex partner. The proposed prospective study of new sexual partnerships of young adults 18-21 years of age focuses on the partnership, not the individual, as the unit of analysis. The purpose of this proposed study is to identify STD/HIV related risk factors and risk markers of partnerships to guide the development of interventions appropriate to the stages of partnerships. The Transtheoretical Model will be adapted and applied to understand adoption and discontinuation of risk reduction and risk enhancing behaviors within partnerships. For example, the model will be applied to understanding progression toward discontinuation of condom use within an ongoing new partnership or understanding decisions to use or not use condoms in other concurrent or subsequent new partnerships. Partnerships of young adults attending STD and family planning clinics will be recruited and both partners followed prospectively through dissolutions and formations of a new and subsequent partnerships. The overall goals of this proposed study aims to identify STD/HIV-related risk factors of partnerships for STD/HIV, and to identify potential interventions appropriate to stage of partnerships for two distinct settings: STD and family planning (FP) clinics. New methods to assess partnerships will be developed that will aid in identifying risky stages of partnerships. The long term goal is to use the findings from the research proposed here to design and conduct stage-of- partnership specific interventions to reduce the risk of STD infection within the partnership, and promote continuation of healthy partnerships. A proposal will subsequently be developed to carry out a randomized controlled trial of the intervention that will assess impact not only on reported behavior change, but on STD acquisition/transmission within the partnership.